Chapter 47 - PowerPoint PPT Presentation

Chapter 47. Animal Development. Development is determined by the zygote’s genome and differences between embryonic cells Cell differentiation is the specialization of cells in structure and function

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This reaction induces a rise in Ca2+from the egg’s ER into the egg’s cytosol. This causes cortical granules in the egg to fuse with the plasma membrane and discharge their contents. This leads to swelling of the perivitelline space, hardening of the vitelline layer, and clippling of sperm binding receptors.

These changes cause formation of a fertilization envelope that functions as a longer-term slow block to polyspermy.

The sharp rise in Ca2+ in the egg’s cytosol increases the rates of cellular respiration and protein synthesis by the egg cell

With these rapid changes in metabolism, the egg is said to be activated

Sperm cells do not contribute any materials required for activation. The unfertilized eggs of many species can be artificially activated by the injection of Ca2+ or by a variety of mildly injurious treatments, such as temperature shock.

LE 47-5 adhere to molecules of a specific receptor proteins on the egg’s surface.

A fluid-filled cavity called the blastocoel begins to form within the morula and is fully formed in the blastula, a hollow ball of cells.

During cleavage, different regions of the cytoplasm end up in separate blastomeres. These regions may contain different cytoplasmic determinants, in many species this partitioning sets the stage for subsequent developmental events.

Gastrulation rearranges the cells of a blastula into a three-layered embryo, called a gastrula, which has a primitive gut.

Varies from one animal to another, the process is driven by change in cell motility, changes in cell shape, and changes in cellular adhesion to other cells and to molecules of the extracellular matrix.

Because all vertebrate embryos required an aqueous environment for development, embryos of birds, other reptiles, and mammals develop in a fluid-filled sac in a shell (birds & reptiles) or the uterus (marsupials & eutherian)

Organisms with these adaptations are called amniotes

In these organisms, the three germ layers also give rise to the four membranes that surround the embryo